Understanding the discharge behavior of an ultra-high-purity Mg anode for Mg–air primary batteries

Abstract

This work used both experiments and modeling methods to understand some critical issues of ultra-high-purity (UHP) Mg discharge behavior for Mg–air primary batteries. The charge transfer resistance is the main internal anodic resistance instead of the resistance due to discharge products. The anodic hydrogen reaction was the only reason for the anodic efficiency drop for the UHP Mg anode. A uni-positive Mg⁺ mechanism explained the anodic hydrogen reaction and two morphologies of discharge products. The UHP Mg had a strong preferred dissolution orientation during discharge at a low applied current density, which tended to disappear with increasing current density. The strongly oriented dissolution of Mg increased the apparent charge transfer resistance of the Mg anode.